Determination of fold and fault geometries from faultrelated fold study : A case of Hukou fault in NW Taiwan

Transcription

1 1 Determination of fold and fault geometries from faultrelated fold study : A case of Hukou fault in NW Taiwan Presenter : Dwi Febriana Rochmah Adviser : Wen-Jeng Huang Date : 2016/10/20

2 Motivation Fold growth is related to activity of fault in fault-related fold study. Either kinematic or mechanical approach in fault-related fold study consider fold growth by its causative fault. Hukou anticline is a controversial fault-related fold. Moreover, new observation of Hukou Fault discovered an active backthrust apparent surface rupture in the hanging wall approximately 400 m from inferred fault trace (Chu HT et al, 2012).

3 Aims of study To know fault and fold geometries of fault related fold study (Hukou anticline in NW Taiwan). Intend to perform numerical modeling to simulate and evaluate Hukou faultrelated anticline geometry and also Hukou fault slip rate.

4 Study area : Hukou fault in NW Taiwan 4 We are here. Hukou-Taoyuan Tableland. Vertical exaggeration 5x. N

5 Topography of Research Area HK1 and HK2 : Drilling Point

6 Topography of Research Area HK1 and HK2 : Drilling Point

7 Geological Map

8 Geological Setting Alluvium Terrace deposits Chungli Fm. Tientzuhu Fm. Yangmei Fm. Chaomen Member Drilling point GPS Station Base station for total station survey Base station for total station survey +GPS Total station survey line Geophysical survey line Syncline Anticline Chaochin Member Thrust fault Inferred fault Concealed fault

9 Geological Setting Hukou fault orientation is ENE direction, surrounding by lateritic terraces. To the westward, Hukou area is covered by Tertiary deposits Alluvium Drilling point GPS Station Hukou fault length = 21 km Active blind thrust -> Active fault type II (Lin, Q.W. et al, 2007) In eastern part, Hukou area is covered by Yangmei Formation or known in Ho, 1975 & 1986 as Toukoshan Fm. (Chu, HT., 2012) Terrace deposits Base station for total station survey Chungli Fm. Base station for total station survey +GPS Total station survey line Tientzuhu Fm. Geophysical survey line Syncline Yangmei Fm. Anticline Chaomen Member Thrust fault Chaochin Member Inferred fault Concealed fault (Lin, Q.W. et al., 2007)

10 Overview of Hukou Structures Tamsui River Dahan River flow direction is migrated because of Quartenary tectonic activity (Huang, 1995; Wang et al., 2002,; Chen, et al., 2003) Fengshan River Extend to the west 9 km Chen W.S, 2010; Wang Y., 2003 Hukou-Taoyuan Tableland (vertical exaggeration 5x) N

11 Hukou Fault Geometry from Previous Study Lin, Q.W. et al (2007) Y B1 x Chu, H.T. et al (2012) B1 x Wang, Y. (2003) Lin, Y.S. et al (2007) Y

12 Hukou Fault reach the ground surface? Chu, H.T. et al (2012)

13 Potential geometry and sense of movement of macrofaults in (A) reverse and (B) normal basement faults. 13 This schematic block diagram lead us how backthrust fault occurred in thrust fault of this study (Cosgrove & Ameen, 2000).

14 Data and Method Intend to understand precisely by working in the interest area. We can fly UAV, measure bedding attitude in some outcrops, totalstation survey. Our aim research. We also interested to do numerical part in this section.

15 1. Construct A Cross Section 2. Geomorphic Approach 3. Fieldwork 4. Numerical Modeling Hukou-Taoyuan Tableland (vertical exaggeration 5x). N

16 Construct A Cross-Section Profile

17 The Busk Construction (Ramsay, 1987)

18 The Isogon Construction (Ramsay, 1987)

19 Geomorphic Approach : Determine fault scarp or terrace scarp?

20 Example : San Joaquin Hill 1.5 k years 0.8 k years 2 k years Date the ages of marine terraces and measure their heights Uplift rates Invert uplift rates Fault slip rates Fault slip rate: 5 mm/year (Grant et al., 1999)

21 Overview of Hukou Structures Tamsui River Dahan River flow direction is migrated because of Quartenary tectonic activity (Huang, 1995; Wang et al., 2002,; Chen, et al., 2003) ZL ka ZL ka Fengshan River Extend to the west 9 km Chen W.S, 2010; Wang Y., 2003 Hukou-Taoyuan Tableland (vertical exaggeration 5x) TAO A 63.7 ka TAO B 57.1 ka YM ka YM ka YM ka N

22 Taoyuan- Hukou Tableland Area

23 Taoyuan- Hukou Tableland Area Yang (1986) LT 3 LT 5 LT 2 LT 4 LT 1b LH a LH B LT 1a

24 Terrace riser following the shape of present-river flow Next step?

25 Example : Hsinshe Terraces Deformation of the terraces older younger Terrace heights Relief across fold scarps Width of the fold limb (Le Beon et al, 2014)

26 Summary 1. Hukou fault could be not classified as active fault type II. 2. In previous study, geometry of Hukou fault has several models such as (a) fault bend fold and (b) fault propagation fold. In this study, a new geometries model for Hukou fold must be proposed to answer this issues. Hukou-Taoyuan Tableland (vertical exaggeration 5x). N

27 27 Thank you for listening! 謝謝聆聽

28 Resistivity survey and Drilling Site (Lin, Q.W. et al, 2007)

29 Northwestern Taiwan Evolution by Meng (1965) Primary Tectonic Arc - In the subsiding arc zone, Toukoshan gravel all over following the shape of primary tectonic arc. - Metamorphic rocks is folded to east-west direction in north wing of primary tectonic arc Uplifted arc zone where Pliocene and Miocene Folded formation exposed Inner uplifted arc zone where Pre-Neogene folded formation exposed. a b c d

30 Secondary Tectonic Arc Northwestern Taiwan Evolution by Meng (1965)